Reports have been made on obtention of antitumor substances from various species of basidiomycetous fungi in recent years. These substances show a significant antitumor effect in intraperitoneal administrations, but they prove to be extremely low in antitumor activity when administered orally. Therefore, although these substances could be of much interest for scientific studies, they have little practical utility.
In the course of our studies on the extracts from various species of basidiomycetous fungi and cultures thereof by use of an aqueous solvent, we found that the refined products prepared from the extracts obtained by a basidiomycetous fungus belonging to the genus Coriolus of Polyporaceae or cultures thereof (including the media used for cultivation) have an excellent antitumor activity not only in intraperitoneal administrations but also in oral administrations, and we further carried forward our studies on the active components of these extracts.
We have now succeeded in isolating the active substances having the antitumor activity from the following process: a solution obtained by concentrating a purified aqueous solution of the extract from a fungus of the genus Coriolus or cultures thereof with an aqueous solvent is saturated with ammonium sulfate and the thus-produced precipitate is desalted and then passed through a column packed with an ion exchanger, such as for example a diethylaminoethyl (DEAE) cellulose column, to adsorb and remove the nitrogenous component, and after repeating the operations mentioned above if necessary, the eluate is desalted and dried. We also succeeded in elucidating the characteristic properties of these active substances and attained this invention on the basis of these findings.